ClassCastException: java.util.Vector

Question

I'm trying to get a list of records(products) from the dataBase and print them into a jsp page.
Here is the code-
Method in session bean to get the records-
public List<Entity.Products> getProducts(int categoryId)
      Query query=manager.createNativeQuery("select * from products  where categoryId="+categoryId);
      return (List<Entity.Products>)query.getResultList();
    }I put the result in the request (in a servlet)-
   request.setAttribute("products",productsManagement.getProducts(categoryId));JSP page-
      <%
         java.util.List<Entity.Products> products=(java.util.List<Entity.Products>) request.getAttribute("products");
          for(Entity.Products product : products)
           %>
        <A href=""><%=product.getProductName()%></A>
           <%
           %>The problen is that i'm getting the error-
java.lang.ClassCastException: java.util.Vector
what is the problem?
Thanks in advanced.

Answer 1

ppl1,
Your problem is with createNativeQuery. Native query returns a Vector of objects. Whereas createNamedQuery (based on JPQL) is smart enough to get the types right. It seems like you want to use createNamedQuery which will allow you to use generics with the Entity type.
For example, with a client
List<Products> products = prodMgr.findAllProducts();
for(Product p : products) {
System.out.println(p");
}The following session bean will work.
// ProdManager
@PersistenceContext EntityManager em;
public List<Product> findAllProducts() {
  // JPQL for findAllDepts: SELECT p FROM Product AS p
  return em.createNamedQuery("findAllDepts");
}If you are committed to native query, use the following on the client and EJB respectively.
List products = prodMgr.findAllProducts();
for( Object obj : products ) {
  System.out.println( obj.toString());
  // use a case "(Product)obj" for field-level access
List findAllProducts() {
return em.createNativeQuery("SELECT * FROM products").getResultList();
}